Multiple user equipment (UE) categories are defined in a current communications system. During communication, UE may report a UE category of the UE to a base station, and the base station then configures a downlink parameter for the UE according to the UE category, where the downlink parameter may include at least one of the following: a maximum number of bits that can be received within one transmission time interval (TTI), where the number of bits is a number of bits of data transmitted in a downlink shared channel (DL-SCH) transport block (the parameter is a first downlink parameter, where the parameter may be represented as: Maximum number of DL-SCH transport block bits received within a TTI), a maximum number of bits, which can be received within one TTI, of data transmitted in one DL-SCH transport block (the parameter is a second downlink parameter, where the parameter may be represented as: Maximum number of bits of a DL-SCH transport block received within a TTI), and a maximum number of bits of data transmitted on a soft channel (the parameter is a third downlink parameter, where the parameter may be represented as: total number of soft channel bits). In this way, it can be known by using the first downlink parameter how many bits of data can be received at most by the UE within one TTI, it can be known by using the second downlink parameter how many bits of data can be received at most by the UE within one TTI in one DL-SCH transport block, and it can be known by using the third downlink parameter how many bits of data can be received at most by the UE on a soft channel.
In a current Long Term Evolution (LTE) release, 64 quadrature amplitude modulation (QAM) is a highest order modulation scheme. However, in practice, to improve spectral efficiency, an order of a modulation scheme of data may also increase gradually, and a higher-order modulation scheme (for example, 256QAM) may be introduced for a base station. For example, when 256QAM is introduced for the base station, the downlink parameter is still determined only according to a UE category. In this way, when UEs supporting different highest order modulation schemes (for example, UE 1 supports a highest order modulation scheme of 64QAM, and UE 2 supports a highest order modulation scheme of 256QAM) exist in a same UE category, the base station can determine the downlink parameter only according to UE, which supports a lowest order in highest order modulation schemes, in the same UE category (for example, the downlink parameter is determined according to the UE 1 supporting a highest order modulation scheme of 64QAM). Therefore, a downlink parameter of UE that can originally support a 256QAM feature is not a downlink parameter determined according to a modulation scheme of 256QAM.
As a result, when the base station and the UE perform downlink transmission, the 256QAM feature cannot be introduced, causing a failure to improve spectral efficiency. It can be seen that, in the foregoing technology, a modulation feature of UE cannot be fully used during a process of downlink transmission and a feature of a highest order modulation scheme supported by the UE cannot be introduced in downlink transmission, which causes a problem that spectral efficiency in downlink transmission is not high.